Weather conditions (Japanese: てんきWeather) are mechanics of the Pokémon games, and have been included in every main series game since Generation II. The weather system was expanded on in Generation III, and again further expanded in Generation IV. In each generation, the weather has been determined either by the location of the battle or the Pokémon involved. Only one weather condition may be present at one time, and only the most recent weather condition will take effect.

In all generations, some moves, such as Thunder and SolarBeam, take advantage of certain weather conditions and have increased power and accuracy. Other moves can directly cause or cease weather, such as Sunny Day and Defog. Beginning in Generation III, some abilities have revolved around weather effects: among other effects, two of Hoenn's legendaries can cause changes in the weather; one other neutralizes it.

History

Generation II

In the second-generation games, three moves were introduced that could change the weather during a battle to alter the playing field slightly. These moves were Sunny Day, which created five turns worth of intense sunlight and allowed a Pokémon to attack with SolarBeam without waiting a turn; Rain Dance, which gave five turns of heavy rain and increased Thunder's accuracy to 100%; and Sandstorm, which made a wild sandstorm that lasted for the same amount of turns. These three moves could change the course of a battle, with intense sun and heavy rain powering up Fire- and Template:Type2 moves, and powering down the other, respectively, and a sandstorm slightly damaging any Pokémon not of the Rock-, Ground-, or Template:Type2s.

Although weather conditions were introduced in this generation, they could not be seen in the overworld until the following set of games.

Generation III

In the third generation, the featured Pokémon in Pokémon Ruby, Sapphire, and Emerald had weather-related abilities. In Ruby, Groudon's ability allowed for intense sunlight to fill the arena until the battle ended, or another weather effect took its place. Likewise, its Sapphire counterpart Kyogre's ability made heavy rain that lasted until the end of the battle or until another weather effect superseded it. Emerald's mascot, however, had a different way of affecting the playing field. While Rayquaza is battling, all effects of the weather are essentially negated, though the actual sunlight/rain/sandstorm/hail remains going. Psyduck and Golduck may also have a similar ability.

Another Pokémon, one which was not available in Ruby or Sapphire without trading, also had a weather-based ability. Tyranitar, once fully evolved from a Larvitar captured in Pokémon FireRed and LeafGreen, has the ability Sand Stream, which causes a sandstorm that lasts until the end of the battle or until another weather-changing move is made. This makes it almost useless for a Tyranitar to have the move Sandstorm itself, as the sandstorm is automatically activated as it comes into battle. Other Pokémon have abilities that benefit from weather that is already in effect, such as Lotad's Swift Swim.

Ruby and Sapphire also debuted another weather-changing move, Hail, which, like Sunny Day, Rain Dance, and Sandstorm before it, changes the weather for five turns, this time to an icy hailstorm. However, this move, and weather effect, have more in common with Sandstorm than with the other two. For the five turns that it's hailing, all Pokémon who are not Template:Type2 are damaged.

During part of the game, Groudon and Kyogre's weather effects could be seen out of battle; some routes also are naturally affected by the weather. Route 119, for example, is often covered in rain; Route 111 has an area in which a sandstorm always blows. These field weather effects would carry through to later games. A location in Hoenn, the Weather Institute is dedicated to the study of weather. The Weather Institute is said to have created a Pokémon that changes with the weather.

Castform

One of the 135 Pokémon released in Generation III was designed to take full advantage of the varying weather conditions. When in a battle where no weather effects are present, Castform, a Template:Type2 Pokémon, is quite unremarkable. However, when any of the effects besides a sandstorm or Shadow Sky are applied, Castform's type and shape change to match the weather, due to its ability, Forecast. Also, when it is leveled up, it learns a move called Weather Ball, which also changes type with the weather, doubling its power when any weather was in effect. Unlike Forecast, Weather Ball's type differs even in a sandstorm, becoming a Template:Type2 move, as well as in Shadow Sky, becoming a Template:Type2 move. However, it should be noted that when battling against Rayquaza, Psyduck, and Golduck, due to their ability to negate all weather effects, Castform is incapable of changing forms and incapable of having a different-typed Weather Ball.

Generation IV

The fourth generation of Pokémon games takes full advantage of the weather conditions. Within the three regions in Pokémon Diamond, Pearl, Platinum, HeartGold, and SoulSilver, there are routes which are constantly rainy, sandy, or (for the first time) covered in snow. A new weather condition was also introduced: fog. Unlike the other conditions, fog cannot be caused by a move; instead there is a move to clear it.

A new ability is introduced that acts as a counterpart to some of the abilities introduced in Generation III. Snow Warning will unleash a hailstorm for the duration of the battle, as Drizzle will cause rain. Four held items were also introduced. These each correspond to a certain weather condition and will increase the duration of the weather condition, if activated by the holder, by three turns.

More interesting things introduced within Generation IV were other conditions that had nothing to do with the weather, but behaved similarly to the weather-activating moves. Like the weather conditions, these moves would affect all Pokémon on the field for five turns, and in various ways. For example, Gravity would rid Levitating Pokémon of their powers, and force both them and Template:Type2s to take damage from Template:Type2 moves, as well as disabling moves like Fly and Bounce, whereas another, Magnet Rise, makes the user invulnerable to Template:Type2 moves, again for five turns. Also, Trick Room alters the dimensions for five turns, making slower Pokémon attack first; and Tailwind increases the Speed of the user's team for three turns.

Fog

Effect: Lowers accuracy of all Pokémon battling, doubles the power of Weather Ball. Honey cannot be used to attract wild Pokémon in patches of grass or in caves. Causes Moonlight, Synthesis, and Morning Sun to recover ¼ of max HP.

On the field

There have been several on-field weather conditions, most of which do the same as another on-field weather condition.

Sun

When the sun shines brightly, the screen brightens and dims alternately. The screen may also turn a shade of orange that flows while dark spots ride across.

Cloudy Skies

Sometimes clouds gather over Route 213, and the whole area gets darker than usual. Rarely happens on Route 212.

Rain

There have been three different rain conditions.

Normal rain: Rain falls. Found in all places where rain is found on the field.

Heavy rain: Rains falls heavily, at a lower angle than in the other. Found occasionally on Route 212.

Thunderstorm: Rain falls heavily, much like the Heavy Rain does, and occasionally, lightning will strike and thunder will rumble. Found on Route 119 as part of the four-day rain-thunderstorm-rain-clear cycle. Found on Route 212 on occasion. It happens on predetermined days, such as the anniversaries of the game's release in each country. It also appeared on St. Patrick's Day; February 29, 2008; and Christmas Day (December 25).

Sandstorm

There has been only one sandstorm condition. Wind whips sand around, making it difficult to see.

Blizzard: Snow whips around, making it difficult to see. Found on Route 217, and less often on Route 216.

Diamond dust: Small ice crystals twinkle in the air. Found on certain special days in Snowpoint City and Mt. Silver. Diamond dust, however, does not have the same effect as other snowy conditions in battle and instead has no effect in battle.

Fog

There has been only one fog condition.

Heavy fog: Thick fog blankets everything. Obstacles and Trainers are difficult to see. Can be cleared with Defog.